Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 425 PM EST Wed Dec 01 2021 Valid 00Z Thu Dec 02 2021 - 00Z Sun Dec 05 2021 A stretch of relatively quiet weather is expected to continue, with no widespread heavy snow or significant icing expected for at least a couple more days. Pacific Northwest to the Northern Rockies and High Plains... Days 1-3... Some unsettled weather is expected to return the region by this evening as a series of shortwaves embedded within fast zonal flow move across the region, pushing a frontal boundary slowly south. However, an upstream trough is expected to cutoff the deep moisture feed, keeping amounts light. Dry weather is then expected to return on Friday as a shortwave ridge translates east across the region. The previously noted trough is then forecast to move onshore Friday night into Saturday, bringing better organized precipitation and a greater threat for heavy snow accumulations back into the northern Cascades and the northwestern Montana ranges. On Saturday, models show a strong low-to-mid level frontogenesis band, with some potential for significant snow, setting up along the U.S.-Canada border from eastern Montana to western North Dakota. ...Great Lakes to the Northeast... Days 1-3... For the overnight through Thursday, a system dropping southeast across southern Saskatchewan is forecast to track north of the Great Lakes through Ontario and into southern Quebec. This system is expected to produce windy conditions and some snow at the onset across the interior Northeast, but little to no significant snowfall accumulations through late Thursday. As the system moves into Atlantic Canada Thursday night, low level winds veering westerly to northwesterly will support some lake effect snow showers and upslope snows across the northern Adirondacks, Green and White mountains, but with mostly minor accumulations expected. Dry conditions are expected for much of the region on Friday before another system sliding through central Canada moves into the Great Lakes Friday night. This system is expected to take a slightly more southerly track across the Great Lakes, with northwesterly winds on the backside of the system delivering some greater potential for at least a few inches of snow across the eastern U.P. of Michigan Friday night into Saturday. Then westerly winds are forecast to bring a return of lake effect back into the Tug Hill of New York later during the day on Saturday. For Days 1-3, the probability of significant icing is less than 10 percent. Pereira